package com.zhuss.util;


import java.util.ArrayList;
import java.util.List;

/**
 * @author summer
 * @date 2021/1/10 10:40
 * 自定义List分页工具
 */

public class PageUtils {
    /**
     * 开始分页
     * @param list
     * @param pageNum 页码
     * @param pageSize 每页多少条数据
     * @return
     */
    public static List startPage(List list,Integer pageNum,
                                    Integer pageSize) {
        if (list == null) {
            return new ArrayList();
        }
        if (list.size() == 0) {
            return new ArrayList();
        }

        int count = list.size(); // 记录总数
        int pageCount = 0; // 页数
        if (count % pageSize == 0) {
            pageCount = count / pageSize;
        } else {
            pageCount = count / pageSize + 1;
        }

        int fromIndex = 0; // 开始索引
        int toIndex = 0; // 结束索引

        if (!pageNum.equals(pageCount)) {
            fromIndex = (pageNum - 1) * pageSize;
            toIndex = fromIndex + pageSize;
        } else {
            fromIndex = (pageNum - 1) * pageSize;
            toIndex = count;
        }

        List pageList = list.subList(fromIndex, toIndex);

        return pageList;
    }
}
